This invention relates to semiconductors with residual impurity effects, and, more particularly, to methods and devices by which such impurity effects can be counteracted.
In the fabrication of semiconductor devices, undesired impurity effects are frequently encountered. Such is the case, for example, in the fabrication of junction devices. In these devices a semiconductive material having a prescribed characteristic is brought into contact with another semiconductive material having a different kind of characteristic. In general the overall devices may have numerous junctions. To produce the different materials that give rise to the desired junctions, it is common practice to incorporate prescribed dopants into the materials.
Thus, in the case of a PIN solar cell fabricated from amorphous silicon, it is common practice to begin the formation of the device with a P layer which requires the incorporation of acceptor atoms, such as boron, into the silicon layer that is being formed. The latter can be produced in any of a well known variety of ways, including glow discharge, sputtering, and chemical vapor deposition. In such a case residual boron-containing compounds may be left in the manifold through which silicon vapors flow, or may be deposited on the electrodes or walls of the reaction chamber.
The inevitable result is undesired contamination of subsequent layers formed in the chamber.
Although cleaning procedures could be used in seeking to eliminate the contaminant effect, such procedures are not only time consuming and costly, they also usually fail to sufficiently remove the source of contamination.
Accordingly, it is an object of the invention to counteract the effects of undesired contaminants during the fabrication of semiconductor layers and devices.
Another object is to counteract the effects of residual contaminants which may be present in the apparatus used in the fabrication of semiconductor layers and devices.
Still another object is to achieve the counteraction of undesired contaminant effects during the fabrication of semiconductor layers and devices from amorphous silicon, including such diverse procedures as glow discharge and chemical vapor deposition.
A further object of the invention is to counteract impurity effects at the junction of semiconductor devices. A related object is to avoid the degradation in electric field strength at semiconductor junctions caused by undesired impurity effects.